Ceramic nanocomposites are classified into three types: intragranular, intergranular, and nano/nano composites. Intragranular and intergranular nanocomposites significantly improve mechanical properties such as toughness, strength, and high-temperature resistance. Nano/nano composites exhibit new functions like machinability and superplasticity. The paper discusses the fabrication methods, microstructure, and mechanical properties of these composites, emphasizing the role of nano-sized dispersoids. It highlights that nano-sized SiC and Si3N4 particles enhance mechanical properties by refining grain structure, increasing fracture toughness, and improving high-temperature performance. The study also shows that nano/nano composites can achieve superplastic deformation at high temperatures. The paper concludes that ceramic nanocomposites offer significant improvements in mechanical properties and new functionalities, making them promising materials for structural applications. The future of structural ceramics lies in hybrid composites combining micro and nanocomposites to achieve superstrong and supertough materials. The research was supported by the Japan Ministry of Education.Ceramic nanocomposites are classified into three types: intragranular, intergranular, and nano/nano composites. Intragranular and intergranular nanocomposites significantly improve mechanical properties such as toughness, strength, and high-temperature resistance. Nano/nano composites exhibit new functions like machinability and superplasticity. The paper discusses the fabrication methods, microstructure, and mechanical properties of these composites, emphasizing the role of nano-sized dispersoids. It highlights that nano-sized SiC and Si3N4 particles enhance mechanical properties by refining grain structure, increasing fracture toughness, and improving high-temperature performance. The study also shows that nano/nano composites can achieve superplastic deformation at high temperatures. The paper concludes that ceramic nanocomposites offer significant improvements in mechanical properties and new functionalities, making them promising materials for structural applications. The future of structural ceramics lies in hybrid composites combining micro and nanocomposites to achieve superstrong and supertough materials. The research was supported by the Japan Ministry of Education.